As practiced in the field, foam block construction techniques typically employ a system of plastic foam blocks interconnected by various means to form an integrated structure for receiving liquid concrete. Each block contains a plurality of internal channels to receive liquid concrete. The concrete, upon hardening, provides structural integrity to support the wall. The plastic foam blocks initially act as a structure to retain the liquid concrete. After the concrete has hardened, the plastic blocks remain an integral element of the wall, providing thermal insulation and a smooth surface to which drywall, siding, or other finishes can be attached.
A common means of interconnection is a tongue and groove system, in which the individual blocks are formed with interlocking configurations on their edges. The interlocking edges allow the foam blocks to be assembled into an integrated structure before the liquid concrete is poured into the blocks.
The prior art teaches the use of different materials for the construction of such blocks. Expanded polystyrene (EPS) foam is one favored material for constructing such blocks because it exhibits several important materials characteristics. EPS is easily formable into blocks which possess sufficient strength and rigidity to retain liquid concrete while remaining sufficiently light to be handled manually. EPS provides a high degree of thermal insulation. Furthermore, EPS can be produced to provide a cost-effective alternative to other wall construction techniques.
Such foam block construction techniques have gained limited commercial success. However, certain disadvantages and limitations inherent in the design of prior foam block systems have inhibited the wide-scale commercial use of foam block wall systems.
A principal limitation of such wall systems has been the inability of the means of interconnection to maintain the proper alignment of the individual blocks within the wall system when liquid concrete is poured into the blocks. The pressure of the liquid concrete tends to force the individual blocks out of proper alignment within the integrated wall system. Experience demonstrates that individual blocks are susceptible to misalignment along all three axes. For example, adjacent blocks may buckle or sway under the weight of the concrete, resulting in a wall that is not straight along the horizontal axis. Similarly, if the wall requires blocks to be stacked more than one layer high, the second layer may sway or float, resulting in a wall that is not straight along the vertical axis. The time and expense associated with remedial measures to correct these alignment problems may eliminate any cost advantage derived from the use of foam block systems.
A second limitation is presented when the blocks are designed with interfitting means, such as interlocking tongues and grooves on the edges. If a block is cut or trimmed to a different size, the interlocking edge is lost in the cut. Special operations are then required to create a new interlocking edge. These operations increase construction time and expense.
A further limitation of prior foam block wall systems is the difficulty of attaching structural or external members to the finished wall structure. The foam block surface provides a smooth, flat surface to which drywall or other lightweight finishing materials may be adhesively attached. However, if building codes or structural requirements preclude the use of adhesives, it is necessary to cut away the foam to gain access to the concrete members which provide structural support. This operation results in increased building costs and time.